<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    *{
        padding: 0;
        margin: 0;
    }
   #header,#footer{
     width: 100%;
     background: #333;
   }

   #content{
       display: flex;
       height: 200px;
   }
   .left,.center,.right{
       height: 200px;
   }
   .left{
       width: 200px;
       background: brown;
   }
   .right{
       width: 200px;
       background: cadetblue;
   }
   .center{
       flex: 1;
       background: yellow;
   }
</style>
<body>
    <header id="header">header</header>
    <section id="content">
        <div class="left">left</div>
        <div class="center">center</div>
        <div class="right">right</div>
    </section>
    <footer id="footer">footer</footer>
</body>
</html>